The structure of oxide glasses containing SeO2

The results for glass formation in selenite systems obtained during the las t 20 years are reviewed. For all of them the vitrification regions are situ ated near the SeO2 corner, which is the main glass-former. The structure of model compositions is studied to elucidate the role of the different build ing units in the formation of the amorphous network. The IR spectra of bina ry selenite glasses are compared with those for more complicated compositio ns. It is proven that it is possible to modify the network of selenite glas ses by introducing compatible polyhedra TeO4, TeO3, VO5, BiO6, Mo2O8 or BO3 with SeO3 units. The better glass-forming tendency of compositions between 90 and 50 mol% SeO2 is related to the creation of additional disorder in t he SeO3 chains by involving other structural units in them. These new glass -forming units are capable of transforming the structure into layers or thr ee-dimensional random networks with a low atomic mobility. (C) 2001 Elsevie r Science B.V. All rights reserved.